Housing for piezoelectric transformer device

ABSTRACT

Mount terminals ( 4   a   , 5   a   , 6 ) are formed on end faces of a housing ( 1 ). These mount terminals serve to mount the housing ( 1 ) on a circuit board and also serves as lead electrodes for the outer and output electrodes of a piezoelectric device to be housed in the case. The piezoelectric device is fixed in the housing ( 1 ) by using the lead electrodes ( 4, 5 ) integrally formed with mount terminals ( 4   a   , 5   a ) and projections ( 2, 3 ).

TECHNICAL FIELD

The present invention relates to a housing for a piezoelectrictransformer device, e.g., a housing for mounting a Rosen piezoelectrictransformer on a circuit board.

BACKGROUND ART

Recently, liquid crystal display panels have been widely used as displayunits in notebook personal computers which are easy to carry. Such aliquid crystal display panel incorporates a cold-cathode fluorescentlamp serving as a backlight for backlighting the panel. In order tolight this cold-cathode fluorescent lamp, a high voltage of about 1 kVor more is required. To maintain emission of light, a voltage of aboutseveral hundred volts must be applied.

In such notebook personal computers and similar products, owing to theircharacteristics, the demand for compact inverters for backlights ishigh. In order to meet this demand, piezoelectric transformers are usedas inverter components.

As such a piezoelectric transformer, the piezoelectric transformerdevice (to be referred to as the piezoelectric device hereinafter)having the multilayer structure proposed in Japanese Patent ApplicationNo. 8-52553 filed by the present applicant will be briefly describedbelow with reference to FIGS. 1 to 5.

FIG. 1 is a perspective view showing the piezoelectric device having themultilayer structure previously proposed by the present applicant. FIG.2 is a front view of the piezoelectric device in FIG. 1. FIG. 3 is aplan view of the piezoelectric device in FIG. 1.

A piezoelectric device 106 has an outer shape like the one shown inFIGS. 1, 2, and 3. The right and left half regions of the device will berespectively referred to as the second and first regions hereinafter.

Outer electrodes 101 and 102 as primary (input) electrodes are formed onthe upper surface of the first region. An outer electrode 103 as asecondary (output) electrode is formed on the right end portion of thesecond region. Lead wires 105 are connected to the outer electrodes 101,102, and 103 with solder portions 104.

The internal structure of the first region will be described next. FIG.4 is a sectional view taken along a line I—I of the piezoelectric devicein FIG. 3. FIG. 5 is a sectional view taken along a line II—II of thepiezoelectric device in FIG. 3.

As shown in FIGS. 4 and 5, in the first region, a plurality of innerelectrodes 101 a and 102 a are alternately stacked, and the spacesbetween these inner electrodes are filled with the piezoelectric element106. As shown in FIGS. 4 and 5, in the first region, the plurality ofinner electrodes 101 a are connected to each other through a columnarconductor (to be referred to as an interlevel connection conductorhereinafter) 108 a, and the plurality of inner electrodes 102 a areconnected to each other through an interlevel connection conductor 108b. Circular holes (to be referred to as holes hereinafter) are formed inthe inner electrodes 101 a and 102 a so that the inner electrodes 101 aand 102 a are not connected to each other through the interlevelconnection conductors 108 a and 108 b.

The interlevel connection conductor 108 a extends toward the uppersurface of the first region and is connected to the outer electrode 101.

Similarly, the interlevel connection conductor 108 b extends toward theupper surface of the first region and is connected to the outerelectrode 102.

The piezoelectric device having the above multilayer structure is drivenas follows. First, a high voltage is applied between the outerelectrodes 101 and 102 to polarize the first region in the verticaldirection (direction of thickness). A predetermined voltage is thenapplied between the outer electrode 101 or 102 and the outer electrode103 to polarize the second region in the longitudinal direction. When anAC voltage is applied between the outer electrodes 101 and 102 of thedevice in the polarized state, the piezoelectric element 106 in thefirst region mechanically vibrates in accordance with the piezoelectricmaterial constant unique to the piezoelectric element, the resonancecharacteristics, and the dimensions of the overall device. Thevibrations are converted into a voltage by the piezoelectric element 106in the second region. As a result, a boosted high AC voltage can beextracted from the outer electrode 103.

When such a piezoelectric transformer is to be mounted on a circuitboard, the transformer is generally housed in an insulating container(to be referred to as a housing hereinafter), and the housing is mountedon the circuit board for the following reason. As described above, whenthe piezoelectric transformer operates, the piezoelectric device itselfmechanically vibrates. If this vibration is inhibited when the device ismounted on the circuit board, the output characteristics of thepiezoelectric transformer deteriorate. Therefore, when the piezoelectrictransformer is to be mounted, the device must be supported at portionscorresponding to nodes of the vibrations of the piezoelectric device toprevent the vibrations of the device from being suppressed. In addition,since the secondary output of the piezoelectric transformer is set at ahigh voltage, the entire piezoelectric transformer must be covered withan insulating cover for safety reasons, i.e., preventing contact betweenthe secondary output and other components and preventing the operatorfrom receiving an electric shock.

An example of how the above piezoelectric device is housed in a housinghaving a general structure will be described with reference to FIGS. 6to 10.

FIG. 6 is a perspective view showing a state in which the piezoelectricdevice having the multilayer structure previously proposed by thepresent applicant is housed in a general housing. FIG. 7 is a plan viewof the housing in FIG. 6.

As shown in FIGS. 6 and 7, a housing 107 is a box-like resin containerhaving an upper opening. The housing 107 has a volume enough to preventthe piezoelectric device 106 and the solder portions 104 of the leadwires 105 from protruding from the upper opening of the housing 107 whenthe piezoelectric device 106 is housed in the housing 107. Projections110 for fixing the piezoelectric device 106 in the housing 107 areformed on the inside of the housing 107 at positions corresponding tothe nodes of the vibrations of the piezoelectric device 106. In the caseshown in FIGS. 6 and 7, the respective lead wires 105 extend outsidethrough the holes (the holes may be slits) formed in the end faces inadvance.

A method of housing the piezoelectric transformer in the housing 107 inthis housed state will be described below, together with the mountedstate of the housing on a circuit board.

FIG. 8 is a sectional view taken along a line III—III of the housing inFIG. 6. FIG. 9 is a sectional view taken along a line IV—IV of thehousing in FIG. 6. FIG. 10 is a perspective view showing an example ofhow the piezoelectric transformer is mounted on the circuit board.

When the piezoelectric device 106 is to be housed in the housing 107,the projections 110 are first coated with an adhesive 109. As shown inFIGS. 8 and 9, the piezoelectric device 106 is then housed in thehousing 107 such that the nodes of the vibrations of the piezoelectricdevice 106 coincide with the projections 110. With this process, thepiezoelectric can be supported in the housing 107 at the portionscorresponding to the nodes of vibrations.

The housing is mounted on the circuit board as follows. After theadhesive 109 applied to the projections 110 is hardened, the housing 107is turned upside down and mounted on a circuit board 112, as shown inFIG. 10. The housing 107 is fixed to the circuit board 112 with anadhesive 111. The respective lead wires 105 extending through the aboveholes are connected to the circuit board 112 by soldering.

Other methods of supporting the piezoelectric device and mounting it onthe circuit board, other than those described above, have been proposed(Japanese Patent Laid-Open Nos. 8-32135 and 8-264853).

When the piezoelectric device is to be housed in the above generalhousing, a large number of steps are required, ranging from the step ofhousing the piezoelectric device in the housing to the step ofconnecting the lead wires on the circuit board, resulting in lowproductivity. When terminals to which the lead wires of thepiezoelectric device are connected are to be formed on the housing, andthe housing is to be mounted on the circuit board through the terminals,a large number of steps are required in mounting the housing, resultingin low productivity.

For example, Japanese Patent Laid-Open No. 8-298213 discloses a housingsuperior to the housing having the above structure in terms ofproductivity. According to this housing, connection of the piezoelectricdevice to the circuit board and supporting of the device in the housingare performed by using the same terminals, thereby obviating thenecessity to use lead wires to connect the piezoelectric device to thecircuit board. According to this technique, the piezoelectric device issupported in the housing by using only the elastic characteristics ofthe terminal members (material) formed on the housing. If, therefore, anexternal shock or vibration acts on this housing, the electricconnection between the piezoelectric device and the terminals may bebroken, resulting in instantaneously disconnection.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a housing thatfacilitates a housing process for a piezoelectric transformer device andcan be easily mounted on a circuit board.

In order to achieve the above object, a housing for a piezoelectrictransformer device according to the present invention has the followingarrangement.

There is provided a piezoelectric transformer device housing made of aresin and adapted to house a piezoelectric transformer device havingprimary outer electrodes formed in one plane, wherein a bottom portionof the housing has an opening in which the piezoelectric transformerdevice is inserted, an upper portion of the housing has lead electrodesto apply voltage to the outer electrodes, the lead electrodes beingformed by using elastic members that produce a restoring force when theouter electrodes are brought into contact with the lead electrodes, andportions of two inner side surfaces of the housing at positionscorresponding to nodes of vibrations of the piezoelectric transformerdevice when the piezoelectric transformer device is housed have firstprojections having pawl-like portions on a bottom portion side of thehousing, wherein the piezoelectric transformer device is supported inthe housing by using the lead electrodes, the first projections, and thepawl-like portions of the first projections. This arrangement simplifiesthe steps of housing the piezoelectric transformer device on the primaryside of the housing, and allows the housing to be easily mounted on acircuit board.

The primary side of the piezoelectric transformer device is preferablybrought into contact with the pawl-like portions with the restoringforce produced by the lead electrodes. This allows the primary side ofthe piezoelectric transformer device to be reliably fixed in thehousing.

Preferably, for example, a portion of an inner upper surface of thehousing at a position corresponding to a node of vibrations of thesecondary side of the piezoelectric transformer device when thepiezoelectric transformer device is housed further has a secondprojection, and the secondary side of the piezoelectric transformerdevice is supported in the housing by using the first projections, thepawl-like portions of the first projections, and the second projection.This facilitates the steps of housing the piezoelectric transformerdevice in the secondary side of the housing, and allows the housing tobe easily mounted on the circuit board.

In addition, preferably, the second projection is integrally formed withthe housing to produce a restoring force when the piezoelectrictransformer device is brought into contact with the second projection,and the secondary side of the piezoelectric transfer device is broughtinto contact with the pawl-like portion by using the restoring force.This allows the secondary side of the piezoelectric transformer deviceto be reliably fixed in the housing.

Furthermore, in order to achieve the above object, a housing for apiezoelectric transformer device according to the present invention hasthe following arrangement.

There is provided a piezoelectric transformer device housing made of aresin and adapted to house a piezoelectric transformer device havingprimary outer electrodes formed in one plane, wherein a bottom portionof the housing has an opening in which the piezoelectric transformerdevice is inserted, an upper portion of the housing has lead electrodesto apply voltage to the outer electrodes, the lead electrodes beingformed by using elastic members that produce a restoring force when theouter electrodes are brought into contact with the lead electrodes, andportions of two inner side surfaces of the housing at positionscorresponding to nodes of vibrations of the piezoelectric transformerdevice when the piezoelectric transformer device is housed haveprojections formed in conformity with a shape of side surfaces of thepiezoelectric transformer device in a widthwise direction, wherein thepiezoelectric transformer device is supported in the housing by usingthe projections. This facilitates the steps of housing the piezoelectrictransformer device in the housing, and allows the housing to be easilymounted on a circuit board.

Preferably, the housing is molded with a flexible resin, and thepiezoelectric transformer device is clamped through the projections withrestoring forces produced on the two side surfaces of the housing whenthe piezoelectric transformer device is housed in the housing.

In the housing having either of the above arrangements, preferably, thelead electrodes and mount terminals used to mount the housing on acircuit board are integrally formed, or the case further comprises alead wire connected to a secondary outer electrode of the piezoelectrictransformer device, and a mount terminal used to mount the housing on acircuit board, thereby easily mounting the housing on the circuit board.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing the piezoelectric device having themultilayer structure previously proposed by the present applicant;

FIG. 2 is a front view of the piezoelectric device in

FIG. 1;

FIG. 3 is a plan view of the piezoelectric device in FIG. 1;

FIG. 4 is a sectional view taken along a line I—I of the piezoelectricdevice in FIG. 3;

FIG. 5 is a sectional view taken along a line II—II of the piezoelectricdevice in FIG. 3;

FIG. 6 is a perspective view showing a state in which the piezoelectricdevice having the multilayer structure previously proposed by thepresent applicant is housed in a general housing;

FIG. 7 is a plan view of the housing in FIG. 6;

FIG. 8 is a sectional view taken along a line III—III of the housing inFIG. 6;

FIG. 9 is a sectional view taken along a line IV—IV of the housing inFIG. 6;

FIG. 10 is a perspective view showing a state in which the housing inFIG. 6 is mounted on a circuit board;

FIG. 11 is a perspective view showing a housing according to the firstembodiment of the present invention;

FIG. 12 is a plan view of the housing in FIG. 11;

FIG. 13 is a front view of the housing in FIG. 11;

FIG. 14 is a right side view of the housing in FIG. 11;

FIG. 15 is a bottom view of the housing in FIG. 11;

FIG. 16 is a sectional view taken along a line V—V in FIG. 12;

FIG. 17 is a sectional view taken along a line VI—VI in FIG. 12;

FIG. 18 is a sectional view taken along a line VII—VII in FIG. 12;

FIG. 19 is a perspective view showing the structure of a member obtainedby integrally molding a mount terminal 4 a (5 a) and a lead electrode 4(5);

FIG. 20 is a perspective view showing the structure of a mount terminal6;

FIG. 21 is a perspective view showing the state of the piezoelectricdevice before it is housed in the housing;

FIG. 22 is a view for explaining a state in which the piezoelectricdevice is inserted into the housing;

FIG. 23 is a plan view of the housing housing the piezoelectric device;

FIG. 24 is a bottom view of the housing in FIG. 23;

FIG. 25 is a sectional view taken along a line VIII—VIII in FIG. 23;

FIG. 26 is a sectional view taken along a line IX—IX in FIG. 23;

FIG. 27 is a sectional view taken along a line X—X in FIG. 23;

FIG. 28 is a perspective view showing a housing according to the secondembodiment of the present invention;

FIG. 29 is a plan view of the housing in FIG. 28;

FIG. 30 is a bottom view of the housing in FIG. 28;

FIG. 31 is a sectional view taken along a line XI—XI in FIG. 29;

FIG. 32 is a sectional view taken along a line XII—XII in FIG. 30;

FIG. 33 is a sectional view showing a state in which the piezoelectricdevice 106 is fixed in the housing 21; and

FIG. 34 is a perspective view showing a modification of part of thestructure of the piezoelectric device previously proposed by the presentapplicant.

BEST MODE FOR CARRYING OUT THE INVENTION

Housings for piezoelectric transformer devices according to theembodiments of the present invention will be described in detail belowwith reference to the accompanying drawings.

In each embodiment to be described below, the piezoelectric device isdriven in the λ mode. Obviously, however, the present invention is notlimited to this. For example, the piezoelectric device may be driven inthe λ/2 or 3/2λ mode.

In the following description, for the sake of descriptive convenience,the piezoelectric device having the structure shown in FIGS. 1 to 5 ishoused in the housing of the present invention. Obviously, however, thepiezoelectric device that can be housed in the housing is not limited tothis. For example, a piezoelectric device having inner electrodesprotruding from an end face in the longitudinal direction may be housedin the housing.

First Embodiment

The first embodiment of the present invention will be described belowwith reference to FIGS. 11 to 28. The outer shape of a housing accordingto the first embodiment will be described first.

FIG. 11 is a perspective view showing a housing according to the firstembodiment of the present invention. FIG. 12 is a plan view of thehousing in FIG. 11. FIG. 13 is a front view of the housing in FIG. 11.FIG. 14 is a right side view of the housing in FIG. 11.

FIGS. 11 to 13 show the state of a housing 1 before the piezoelectricdevice is housed therein. The housing 1 of this embodiment has abox-like shape having an opening in the bottom portion. The housing 1 ismainly constituted by a housing body using an insulating resin and aplurality of metal terminals. The piezoelectric device is inserted fromthe bottom surface side of the case. The housing 1 therefore has avolume larger than that of the piezoelectric device to be housedtherein. The right and left half regions of the housing 1 will berespectively referred to as the second and first regions hereinafter.

Two metal mount terminals 4 a and 5 a as first mount terminals areformed on the end face of the first region of the housing 1 in thelongitudinal direction. A metal mount terminal 6 as a second mountterminal is formed on the end face of the second region in thelongitudinal direction. These mount terminals serve to mount the housing1 on a circuit board and to function as the lead electrodes of the outerand output electrodes of the piezoelectric device to be housed in thecase (to be described in detail later).

An opening 7 is formed in the upper portion of the first region of thehousing 1. As shown in FIGS. 11 and 12, in the opening 7, elastic metallead electrodes 4 and 5 in the form of leaf springs are integrallyformed with the housing 1. Projections 2 as first projections are formedon the inside of the first region of the housing 1 at a positioncorresponding to a node of the vibrations of the piezoelectric devicewhen it is housed in the case.

A projection 3 as a second projection made of the same material as thatfor the housing 1 and protruding inside the case is formed on the innerupper surface of the second region of the housing 1. Similar to theprojections 2, this projection 3 is formed at a position correspondingto a node of the vibrations of the piezoelectric device. A slit 8through which a lead wire extends is formed in a side surface of thesecond region. The slit 8 has a width larger than the diameter of thelead wire for connecting the secondary electrode of the piezoelectricdevice to the mount terminal 6 so as not to adversely affect thevibrations of the piezoelectric device.

The internal structure of the housing 1 will be described next. FIG. 15is a bottom view of the housing in FIG. 11. FIG. 16 is a sectional viewtaken along a line V—V in FIG. 12. FIG. 17 is a sectional view takenalong a line VI—VI in FIG. 12. FIG. 18 is a sectional view taken along aline VII—VII in FIG. 12.

Each projection 2 has the shape shown in FIGS. 17 (first region) and 18(second region). The pawl-like portion of each projection 2 on thebottom portion (lower side) of the housing 1 is tapered. In both thefirst and second regions, a distance W between the projections 2 on thetwo inner side surfaces of the housing 1 is equal to the width of thepiezoelectric device to be housed.

As shown in FIG. 17, a distance D1 from the bottom surfaces of the leadelectrodes 4 and 5 to the plane connecting right-angle portions X1 ofthe projections 2 on the two sides of the housing 1 is smaller than thethickness of the piezoelectric device.

As shown in FIG. 18, a distance D2 from the bottom surface of theprojection 3 to the plane connecting right-angle portions X2 of theprojections 2 on the two sides of the housing 1 is smaller than thethickness of the piezoelectric device. Note that the projection 3 ismade of the same material as that for the housing 1, as described above.Since the projection 3 is molded into the shape shown in FIG. 18, itexhibits elasticity against an external force applied from the lowerside in FIG. 18 to the bottom surface of the projection 3.

The mount terminals 4 a and 5 a and the lead electrodes 4 and 5 formedin the first region are integrally molded, as indicated by theperspective view of FIG. 19. In the process of molding the housing 1,these members are embedded in the housing 1 in the state shown in FIGS.15 and 16. In addition, a portion L1 in FIG. 19 is formed at a positioncorresponding to a node of the vibrations of the piezoelectric device.

The mount terminal 6 formed on the end face of the second region has theshape shown in the perspective view of FIG. 20. In the process ofmolding the housing 1, the mount terminal 6 is embedded in the housing 1in the state shown in FIGS. 15 and 16. The mount terminal 6 has aprojection 6 a for holding the lead wire extending from the secondaryelectrode of the piezoelectric transformer.

A procedure for housing the piezoelectric device in the housing 1 willbe described next. In this embodiment, the piezoelectric device 106having the structure shown in FIGS. 1 to 5 is housed in the housing 1 inthe state shown in FIG. 21, in which the lead wire 105 is soldered tothe secondary electrode 103.

More specifically, the piezoelectric device 106 is pressed against thebottom portion of the housing 1. Then, the piezoelectric device 106 isinserted into the housing 1 toward the upper surface of the case untilthe device 106 stops. Since the pawl-like portions of the projections 2of the housing 1 are tapered as described above, when the device ispressed against the bottom portion of the housing 1, the side surfacesof the housing 1 bend outward to allow the device to be easily insertedinto the case, as shown in FIG. 22.

The housing 1 having the piezoelectric device 106 housed therein will bedescribed next. FIG. 23 is a plan view of the housing 1 having thepiezoelectric device housed therein. FIG. 24 is a bottom view of thehousing in FIG. 23. FIG. 25 is a sectional view taken along a lineVIII—VIII in FIG. 23. FIG. 26 is a sectional view taken along a lineIX—IX in FIG. 23. FIG. 27 is a sectional view taken along a line X—X inFIG. 23.

As shown in FIGS. 24 and 25, the piezoelectric device 106 housed in thehousing 1 is supported by the projections 2 of the housing 1 at portionscorresponding to nodes of the vibrations of the device.

The distance D1 in FIG. 17 has changed to a distance D3 in FIG. 26 uponinsertion of the piezoelectric device 106. The relationship between thedistances D1 and D3 is defined as D3>D1. The difference between thedistances D1 and D3 is produced when the lead electrodes 4 and 5 in theform of leaf springs deflect upward in FIG. 26. This deflection amountserves as a force P with which the lead electrodes 4 and 5 push thepiezoelectric device 106 downward in FIG. 26. Since the piezoelectricdevice 106 is brought into contact with the right-angle portions X1 ofthe end portions of the projections 2 with the force P, thepiezoelectric device 106 is fixed in the first region of the housing 1.

Note that the force P produced by the deflection amount is obtained fromthe material and shape of the lead electrodes 4 and 5 by the followingequation:

P[kg]=bh²σ/6L

where b [mm] is the width of each lead electrode, h [mm] is thethickness of each lead electrode, σ [kg/mm²] is the bending stress, andL [mm] is the length of each lead electrode from the fulcrum.

The present applicant made an experiment for checking the magnitude ofthe force P that was required to stably fix the piezoelectric device 106in the housing 1 without causing disconnection upon application of anexternal shock or vibration. As a result, it was found that a force ofabout 4 [kg] was required to fix the piezoelectric device 106 of aweight of about 10 [g] in the housing 1. This force is produced by thelead electrodes 4 and 5 and the projection 3 and is used to fix thepiezoelectric device 106.

While the piezoelectric device 106 is housed in the housing 1, thebottom surface portion of the projection 3 is in contact with the uppersurface of the piezoelectric device 106, as shown in FIG. 27, and theprojection 3 is deflecting upward in FIG. 27. For this reason, a forceP′ for pushing the piezoelectric device 106 downward acts on the bottomsurface portion of the projection 3. Since the piezoelectric device 106is brought into contact with right-angle portions X2 of the end portionsof the projections 2 with the force P′, the piezoelectric device 106 canbe fixed in the second region of the housing 1.

While the piezoelectric device 106 is housed in the housing 1, the leadelectrodes 4 and 5 are in contact with the outer electrodes 101 and 102as the primary electrodes of the piezoelectric transformer. When,therefore, an input voltage is applied to the mount terminals 4 a and 5a, a voltage can be applied to the primary electrodes of thepiezoelectric device 106.

The lead wire 105 soldered to the outer electrode 103 of thepiezoelectric device 106 extends outside the housing 1 through the slit8 in FIG. 14 and is connected to the mount terminal 6. This lead wire105 is soldered to the mount terminal 6. In this embodiment, theprojection 6 a is formed on the mount terminal 6 as shown in FIG. 20 tofacilitate soldering.

The housing 1 in the state shown in FIGS. 23 to 25 is mounted on thecircuit board by soldering the mount terminals 4 a, 5 a, and 6 topatterns formed on the circuit board.

Note that the formation of the opening 7 described in FIGS. 11 and 12may be omitted to decrease the number of steps of designing a mold forthe housing 1 and the manufacturing cost. Obviously, however, theopening 7 is preferably formed to facilitate a check on the connectionstate between the lead electrodes and the outer electrodes of thepiezoelectric device 106 while the piezoelectric device 106 is housed inthe housing 1 and to allow easy connection between the lead electrodesand the outer electrodes of the piezoelectric device 106 with aconductive adhesive or by soldering, as needed, through the opening 7 soas to improve the reliability of the piezoelectric transformer.

When the opening 7 is to be formed in the housing 1, part or all of theopening 7 is preferably covered with an insulating sheet inconsideration of safety after the piezoelectric device 106 is housed inthe housing 1 and its stored state is checked.

<Effects of First Embodiment>

As described above, according to the housing for the piezoelectrictransfer device according to this embodiment, the piezoelectric device106 can be easily housed in the housing 1 by only pushing the deviceinto the case from the bottom portion side of the case. Morespecifically,

(1) In the first region, the piezoelectric device 106 is brought intocontact with the pawl-like portions of the projections 2 on the bottomportion of the housing 1 and is fixed thereto with the force P producedupon deflection of the elastic lead electrodes 4 and 5. This allows thepiezoelectric device 106 to be fixed in the housing 1 without using anyadhesive.

(2) In the second region, the piezoelectric device 106 is brought intocontact with the pawl-like portions of the projections 2 on the bottomportion of the housing 1 and is fixed thereto with the force P′ producedupon deflection of the projection 3 made of the same material as thatfor the housing 1. This allows the piezoelectric device 106 to be fixedin the housing 1 without using any adhesive.

(3) The lead electrode 4 (5) and the mount terminal 4 a (5 a) areintegrally formed by using an elastic metal material, and the leadelectrodes are brought into contact with the outer electrodes 101 and102 of the piezoelectric device 106, thereby omitting the step ofsoldering the primary lead wires of the piezoelectric device 106.

(4) The housing 1 is designed such that the housing 1 housing thepiezoelectric device 106 can be mounted on the circuit board byconnecting the mount terminals 4 a, 5 a, and 6, i.e., the three portionsto the circuit patterns on the circuit board. This can omit the step ofbonding the housing 1 on the circuit board with an adhesive.

(5) The formation of the opening 7 in the upper portion of the housing 1facilities a check on the connection state between the lead electrodesand the outer electrodes of the piezoelectric device 106 while thepiezoelectric device 106 is housed in the housing 1. In addition, withthe opening 7, the lead electrodes can be easily connected to the outerelectrodes of the piezoelectric device 106 with a conductive adhesive orby soldering, as needed.

Second Embodiment

The second embodiment of the present invention will be described withreference to FIGS. 28 to 33.

The outer shape of a housing 21 will be described first. FIG. 28 is aperspective view showing the housing according to the second embodimentof the present invention. FIG. 29 is a plan view of the housing in FIG.28.

In the housing 21 shown in FIGS. 28 and 29, lead electrodes 24 and 25,mount terminals 24 a and 25 a, and amount terminal 26 respectively havethe same structures and functions as those of the lead electrodes 4 and5, the mount terminals 4 a and 5 a, and the mount terminal 6 in thefirst embodiment described above, and hence a description thereof willbe omitted.

The structural characteristics of the housing 21 according to thisembodiment will be described next. FIG. 30 is a bottom view of thehousing in FIG. 28. FIG. 31 is a sectional view taken along a line XI—XIin FIG. 29. FIG. 32 is a sectional view taken along a line XII—XII inFIG. 30.

As shown in FIGS. 30 to 32, in this embodiment, the width of the housing21 on the bottom portion side is smaller than the width of the housing21 on the upper side.

In addition, in this embodiment, projections 22 as first projections areused in both the first region (FIG. 31) and the second region (FIG. 32)so as to fix a piezoelectric device 106 in the housing 21.

As in the first embodiment, the projections 22 have pawl-like portionsformed on the bottom portion side of the housing 21, the pawl-likeportions have right-angle portions X1 and X2 with which thepiezoelectric device 106 comes into contact. The pawl-like portions arealso tapered.

The projections 22 on the upper surface side of the housing 21 also haveright-angle portions Y1 and Y2 with which the piezoelectric device 106is brought into contact. The housing 21 therefore has no projection 3 inthe first embodiment.

In this embodiment, with this structure of the housing 21, after thepiezoelectric device 106 is inserted into the housing 21, thepiezoelectric device 106 is fixed by using a restoring force Pr thattries to restore the housing 21 to the shape shown in FIGS. 30 to 32.Unlike this embodiment, the first embodiment uses the force P producedupon deflection of the lead electrodes and the force P′ produced upondeflection of the resin projection.

FIG. 33 is a sectional view taken along a line XI—XI in FIG. 29, showinga state in which the piezoelectric device 106 is fixed in the housing21. When the piezoelectric device 106 is inserted into the housing 21, awidth W2 of the housing 21 on the bottom side shown in FIGS. 31 and 32increases to a width W2′, as shown in FIG. 33. As a result, the shape ofthe bottom portion of the housing 21 becomes almost the same as theshape (rectangle) of the upper surface portion of the case. In thisstate, since the housing 21 itself is molded into the shape shown inFIGS. 30 to 32, the side surfaces of the housing 21 in the longitudinaldirection are deflecting outside the case. The projections 22 can clampthe piezoelectric device 106 in the directions of the arrows in FIG. 33with the resorting force Pr that tries to restore the side surfaceportions to the original shape. This allows the piezoelectric device 106to be fixed in the housing 21 with the projections 22 and theright-angle portions X1, X2, Y1, and Y2 at the portions corresponding tonodes of the vibrations of the piezoelectric device 106.

In this embodiment as well, an opening 27 can be omitted. However, theopening 27 is preferably formed for the reasons described in the firstembodiment.

<Effects of Second Embodiment>

(1) Since the restoring force Pr that tries to restore the entire sidesurface portions of the housing 21 to the original shape is used to fixthe piezoelectric device 106, the device can be fixed with a largerforce than that in the first embodiment.

(2) Since the restoring force Pr is used to fix the piezoelectric device106, the formation of the projection 3 in the first embodiment can beomitted. This reduces the number of steps of designing a mold for thehousing 1 and the manufacturing cost.

(3) Since the resorting force Pr is used to fix the piezoelectric device106, members having less elasticity than the lead electrodes 4 and 5 inthe first embodiment can be used for the lead electrodes 24 and 25. Thisreduces the unit cost of members constituting a piezoelectrictransformer.

Since the projections 22 are tapered, the piezoelectric device 106 canbe easily housed in the housing 21. In addition, the housing 21 can bemounted on the circuit board with the three mount terminals. Theseeffects are the same as those of the first embodiment, in addition tothe effects obtained by forming the opening 27.

<Modification of Embodiment>

In each embodiment, the piezoelectric device having the structure shownin FIG. 21 is used as an example of a piezoelectric device to be housed.However, the structure in which the outer electrode 103 is formed on theend portion of the piezoelectric device 106 and the lead wire 105 isconnected to the outer electrode 103 is not an optimal structure fromthe point of view that the mechanical vibrations of the piezoelectricdevice itself should not be suppressed as much as possible, and thenumber of manufacturing steps for mass production should be minimized.For example, therefore, the piezoelectric device having the structureshown in FIG. 34, which is based on the structure of the piezoelectricdevice disclosed in Japanese Patent Application No. 9-148232 previouslyfiled by the present applicant, may be used. Note that Japanese PatentApplication No. 9-148232 was not laid open to public inspection when thepresent application was filed. In addition, the present applicant filedInternational Application No. PCT/JP97/02383 (and Taiwanese PatentApplication No. 86109729) including the present application as adeclaration of priority.

FIG. 34 is a perspective view showing a modification of part of thestructure of the piezoelectric device previously proposed by the presentapplicant.

Referring to FIG. 34, the left inner region of a piezoelectric device206 has the same structure as that of the piezoelectric device 106described above. A mesh-like secondary output electrode is formed in aninner region near the right end portion of the piezoelectric device 206,and an outer electrode 203 as a lead electrode for the output electrodeis formed on the surface of the secondary side of the device at aportion corresponding to a node of the vibrations of the piezoelectricdevice 206. As shown in FIG. 34, the outer electrode 203 and themesh-like secondary output electrode are connected to each other throughthe lead electrode formed on the surface of the device. Therefore, onlyprimary input electrodes 201 and 202 respectively connected to the twoinner electrode groups, the outer electrode 203, and the lead electrodethat connects the outer electrode 203 to the mesh-like secondary outputelectrode are exposed on the same upper surface of the piezoelectricdevice 206.

Consider a case in which the piezoelectric device 206 having thisstructure is housed in the housing of each embodiment described above.

In this case, the housing in which the piezoelectric device 206 is to befixed may have the following structure based on the structure of thehousing 1 or 21 described above. More specifically, the first region ofthe housing, which is to be connected to the input electrodes 201 and202, may have the same structure as the first region of the housing 1 or21. Obviously, the second region of the housing, which is to beconnected to the outer electrode 203 on the secondary side, may have onemember (see FIG. 19) obtained by integrally forming a mount terminal anda lead electrode in conformity with the structure of the second regionof the housing 1 or 21. The concept of the present invention cantherefore be easily applied to a case in which a piezoelectric devicehaving a structure similar to that of the piezoelectric device 206 isused. In addition, the lead wires on the secondary side of thepiezoelectric device can be omitted. This can reduce the number of stepsfor mass production. In addition, the proper operation of the device asa piezoelectric transformer can be ensured.

As has been described above, according to each embodiment describedabove, there is provided a housing that facilitates the housing processfor a piezoelectric transformer device and can be easily mounted on acircuit board. This can reduce the mass production cost of piezoelectrictransformers.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the claims.

What is claimed is:
 1. A housing for a piezoelectric transformer devicemade of a resin and adapted to house the piezoelectric transformerdevice (106) having primary outer electrodes (101, 102) formed in oneplane, characterized in that a bottom portion of said housing (1) has anopening in which said piezoelectric transformer device is inserted; anupper portion of said housing has lead electrodes (4, 5) to applyvoltage to said outer electrodes, said lead electrodes being formed byusing elastic members that produce a restoring force when said outerelectrodes are brought into contact with said lead electrodes; andportions of two inner side surfaces of said housing at positionscorresponding to nodes of vibrations of said piezoelectric transformerdevice when said piezoelectric transformer device is housed, have firstprojections (2) having pawl-like portions (X1, X2) on a bottom portionside of said housing, wherein said piezoelectric transformer device issupported in said housing by using said lead electrodes, said firstprojections, and said pawl-like portions of said first projections. 2.The housing case according to claim 1, characterized in that a primaryside of said piezoelectric transformer device is brought into contactwith said pawl-like portions with the restoring force produced by saidlead electrodes.
 3. The housing according to claim 1, characterized inthat a portion of an inner upper surface of said housing at a positioncorresponding to a node of vibrations of the secondary side of saidpiezoelectric transformer device when said piezoelectric transformerdevice is housed further has a second projection (3), and the secondaryside of said piezoelectric transformer device is supported in saidhousing by using said first projections, said pawl-like portions of saidfirst projections, and said second projection.
 4. The housing accordingto claim 3, characterized in that said second projection is integrallyformed with said housing to produce a restoring force when saidpiezoelectric transformer device is brought into contact with saidsecond projection, and the secondary side of said piezoelectric transferdevice is brought into contact with said pawl-like portion by using therestoring force.
 5. The housing according to claim 1, characterized inthat said pawl-like portions are tapered to facilitate insertion of saidpiezoelectric transformer device into said housing.
 6. A housing for apiezoelectric transformer device made of a resin and adapted to housethe piezoelectric transformer device (106) having primary outerelectrodes (101, 102) formed in one plane, characterized in that abottom portion of said housing (21) has an opening in which saidpiezoelectric transformer device is inserted; an upper portion of saidhousing has lead electrodes (24, 25) to apply voltage to said outerelectrodes, said lead electrodes being formed by using elastic membersthat produce a restoring force when said outer electrodes are broughtinto contact with said lead electrodes; and portions of two inner sidesurfaces of said housing at positions corresponding to nodes ofvibrations of said piezoelectric transformer device when saidpiezoelectric transformer device is housed have projections (22, X1, X2,Y1, Y2) formed in conformity with a shape of side surfaces of saidpiezoelectric transformer device in a widthwise direction, wherein saidpiezoelectric transformer device is supported in said housing by usingsaid projections.
 7. The housing according to claim 6, characterized inthat portions of said projections which are located on a bottom side ofsaid housing are tapered to facilitate insertion of said piezoelectrictransformer device into said housing.
 8. The housing according to claim6, characterized in that said housing is molded with a flexible resin,and said piezoelectric transformer device is clamped through saidprojections with restoring forces produced on said two side surfaces ofsaid housing when said piezoelectric transformer device is housed insaid housing.
 9. The housing according to claim 1, characterized in thatsaid lead electrodes and mount terminals (4 a, 5 a, 24 a, 25 a) used tomount said housing on a circuit board are integrally formed.
 10. Thehousing according to claim 1, characterized in that one end portion ofsaid lead electrode comes into contact with said outer electrode at aposition corresponding to a node of vibrations of the primary side ofsaid piezoelectric transformer device.
 11. The housing according toclaim 1, characterized by further comprising a lead wire (105) connectedto a secondary outer electrode (103) of said piezoelectric transformerdevice, and a mount terminal (6, 26) used to mount said housing on acircuit board.
 12. The housing according to claim 11, characterized inthat said mount terminal includes a projection (6 a, 26 a) for holdingthe lead wire.
 13. The housing according to claim 1, characterized inthat an opening (7, 27) is formed above said lead electrode of saidhousing.
 14. The housing according to claim 13, characterized in thatpart or all of the opening is covered with an insulating sheet.
 15. Thehousing according to claim 6, characterized in that said lead electrodesand mount terminal (4 a, 5 a, 24 a, 25 a) used to mount said housing ona circuit board are integrally formed.
 16. The housing according toclaim 6, characterized in that one end portion of said lead electrodecomes into contact with said outer electrode at a position correspondingto a node of vibrations of the primary side of said piezoelectrictransformer device.
 17. The housing according to claim 6, characterizedby further comprising a lead wire (105) connected to a secondary outerelectrode (103) of said piezoelectric transformer device, and a mountterminal (6, 26) used to mount said housing on a circuit board.
 18. Thehousing according to claim 17, characterized in that said mount terminalincludes a projection (6 a, 26 a) for holding the lead wire.
 19. Thehousing according to claim 6, characterized in that an opening (7, 27)is formed above said lead electrode of said housing.
 20. The housingaccording to claim 19, characterized in that part or all of the openingis covered with an insulating sheet.